Grading tools, systems, and methods

ABSTRACT

The present subject matter relates to devices, systems, and methods for shaping complex contours using a grading tool that is pushed or pulled along the ground. The grading tool can include a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile and a coupling element connected to the blade and configured to adjust an angle at which the blade contacts a ground surface.

TECHNICAL FIELD

The subject matter disclosed herein relates generally to systems and methods for earthmoving or ground material shaping tasks. More particularly, the subject matter disclosed herein relates to devices, systems, and methods for shaping complex contours using a tool that is pushed or pulled along the ground.

BACKGROUND

Roads composed of gravel, dirt, aggregates, or other gradable materials must be periodically maintained to account for displacement of material due to weather, traffic, or other causes. Performing routine maintenance on gravel roads typically requires an array of service equipment to perform different aspects of the maintenance project. For example, a common lineup of equipment for this service can include one ten wheel truck for moving equipment (1 engine, 10 tires, weighs 22,000 pounds), one trailer (8 tires, weighs 12,000 pounds), one road grader (1 engine, 6 tires, weighs 36,000 pounds), and one loader backhoe (1 engine, 4 tires, weighs 17,000 pounds). It would be desirable for a system to be able to effectively perform such earthmoving or ground material shaping tasks without requiring multiple vehicles or machines to complete the maintenance.

SUMMARY

In accordance with this disclosure, devices, systems, and methods for shaping complex contours using a tool that is pushed or pulled along the ground are provided. In one aspect, a grading tool is provided. The grading tool can include a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile and a coupling element connected to the blade and configured to adjust an angle at which the blade contacts a ground surface.

In another aspect, a system for grading a ground surface includes a grading tool having a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile and a coupling element connected to the blade and configured to adjust an angle at which the blade contacts a ground surface, and a draft linkage assembly is connected at a first end to the grading tool and at a second end to machine or vehicle. In this configuration, the draft linkage is configured to move the grading tool relative to the machine or vehicle.

In another aspect, a method for grading a ground surface involves positioning a grading tool at or near a ground surface to be graded, the grading tool comprising a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile, adjusting an angle of the blade with respect to the ground surface, and moving the blade with respect to the ground surface to produce a desired surface configuration.

Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present subject matter will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which:

FIG. 1 is a perspective side view of a grading tool according to an embodiment of the presently disclosed subject matter.

FIG. 2 is a top plan view of a grading tool according to an embodiment of the presently disclosed subject matter.

FIG. 3 is a bottom plan view of a grading tool according to an embodiment of the presently disclosed subject matter.

FIG. 4 is a top plan view of a grading tool according to an embodiment of the presently disclosed subject matter.

FIGS. 5A and 5B are front elevation views of a grading tool in various orientations relative to a ground surface to be graded according to embodiments of the presently disclosed subject matter.

FIGS. 6 through 7B are side views of a grading tool engaging a ground surface according to embodiments of the presently disclosed subject matter.

FIGS. 8A through 8C are side views of a variable height device for a grading tool according to an embodiment of the presently disclosed subject matter.

FIG. 9 is a perspective rear view of a grading tool according to an embodiment of the presently disclosed subject matter.

FIG. 10 is a side schematic view of a grading tool engaging a ground surface according to embodiments of the presently disclosed subject matter.

FIGS. 11A and 11B are a side perspective view and a side view, respectively, of a coupling element for a grading tool according to an embodiment of the presently disclosed subject matter.

FIG. 12 is a rear view of a coupling element for a grading tool according to an embodiment of the presently disclosed subject matter.

FIGS. 13 through 15 are perspective side views of various systems that incorporate the grading tool onto a vehicle according to embodiments of the presently disclosed subject matter.

DETAILED DESCRIPTION

The present subject matter provides devices, systems, and methods for shaping complex contours using a tool that is pushed or pulled along the ground. In one aspect, the present subject matter provides a grading tool that is movable to interact with a ground surface in a variety of different modes. Referring to embodiments shown in FIGS. 1 and 2 , a grading tool, generally designated 100, includes a ground-engaging blade 110 comprising a leading edge 112 having a substantially concave profile and a trailing edge 116 having a substantially convex profile. The grading tool 100 can further include a coupling element 120 connected to the blade 110 and configured to adjust an angle at which the blade contacts a ground surface.

The blade 110 can be constructed of a material having a sufficient strength and/or hardness selected to resist deformation when deployed for earthmoving or ground material shaping tasks. In some embodiments, for example, the blade 110 is formed from a steel plate or other substantially rigid material. Further, as shown in FIG. 3 , in some embodiments, a leading edge 112 of the blade 110 is reinforced with one or more cutting edge 115 that is bolted or otherwise attached to the leading edge 112. In some embodiments, the one or more cutting edge 115 is composed of hardened steel, a wear resistant alloy steel with manganese, chromium, and nickel, or any of a variety of other materials selected to resist deformation when encountering gravel, dirt, aggregates, debris, or other materials during earthmoving or ground material shaping tasks.

In some embodiments, the one or more cutting edge 115 can be positioned with respect to the blade 110 to help define an angle at which the blade 110 can engage the ground surface. For example, in some embodiments, the one or more cutting edge 115 can be attached at any of a range of angles from about 45 degrees to about 75 degrees. Further in some embodiments, the one or more cutting edge 115 can extend beyond a bottom surface of the leading edge 112 of the blade 110 to protect or otherwise shield the blade 110 from damage when the leading edge 112 is positioned to engage a ground surface. This difference in extent of the one or more cutting edge 115 relative to the leading edge 112 of the blade 110 can also represent a maximum amount of wear the one or more cutting edge 115 can incur before replacement is recommended.

Further, in some embodiments, the trailing edge 116 of the blade 110 is reinforced with one or more wear surfaces 119 that are bolted or otherwise attached to the trailing edge 116. In some embodiments, each of the one or more wear surfaces 119 is a discrete material section that can be independently replaced as needed. For example, in some embodiments, the one or more wear surfaces 119 can include a plurality of steel surfaces attached to the trailing edge 116 in an arrangement that substantially follows the substantially convex profile of the trailing edge 116. In some particular configurations, each of the one or more wear surfaces 119 is a steel plate that has a width of about 4 inches, a length of about 12 inches, and a thickness of about 2 inches. Similar to the one or more cutting edge 115, the one or more wear surfaces 119 can be composed of hardened steel, a wear resistant alloy steel with manganese, chromium, and nickel, or any of a variety of other materials selected to resist deformation when encountering gravel, dirt, aggregates, debris, or other materials during earthmoving or ground material shaping tasks.

Regardless of the particular construction of the blade 110, as indicated above, the leading edge 112 has a substantially concave profile. In particular, when the blade 110 is set flat on the ground and viewed from directly above, such as is shown in FIGS. 2 and 4 , the leading edge 112 forms a concave shape, with forward corners 113 being swept forward (i.e., in a primary direction of travel D of the tool 100) relative to a middle front portion 114. In some embodiments, the concave shape is symmetrical with respect to a centerline C of the tool 100, although those having ordinary skill in the art will recognize that any of a variety of asymmetrical shapes for blade 110 can be useful in particular applications.

The concave portion of the blade 110 may be a continuous curved surface (See, e.g., FIG. 2 ) or it may be constructed of a series of flat surface segments (See, e.g. FIG. 1 ) to facilitate cutting edge manufacturing and servicing. In a further alternative embodiment shown in FIG. 4 , the concave section of the blade is a combination of a constant radius curve in a middle portion 112 a of the blade (e.g., extending about 60% of the distance from a centerline C of the tool 100), and an outer portion 112 b on each end blends into an exponential curve as it sweeps to the forward corners 113, which are the forwardmost points of the concave shape. The radius of curvature of the middle portion 112 a is in a range from about 4 to about 7 times the total width of the blade 110. In this regard, for example, where the blade 110 is 8 feet wide, the radius of curvature of the middle portion 112 a is in a range from about 32 feet to about 56 feet. The outer portions 112 b form an exponential curve that blends into the constant radius of the middle portion 112 a and comes to a point at the forward corners 113.

In some embodiments, the concave curve can be approximated into a plurality of discrete flat cutting edges, which can optimize the blade shape for cutting edge servicing. In the embodiment shown in FIG. 3 , for example, the leading edge 112 includes two interior portions positioned on either side of the centerline C that are angled inwardly to generally follow a constant radius section, and an exterior portion on either side of the interior portions are more steeply angled to approximate the outer, exponential sections.

Regardless of the particular shape of the leading edge 112, in some embodiments, a width-to-depth ratio of the blade 110 is in a range from about 3-to-1 to about 4-to-1. In this way, the depth of the concave shape can be about ⅔ of the total front-to-back dimension of the blade 110 with a remaining ⅓ forming the blade itself at its center. In some particular examples, where the blade 110 is about 8 feet wide, such a relationship can result in a front-to-back dimension from the furthest forward point of the leading edge 112 (e.g., at forward corners 113) to the furthest rearward point of the trailing edge 116 can be about 30 inches compared to a dimension of the blade 110 at or about the centerline C of about 10 inches. Because the blade's concave-convex shape is not inherently tied to a specific set of proportions, however, those having ordinary skill in the art will recognize that these proportions can be varied as desired to accommodate different applications and associated machines.

This concave profile can provide multiple advantageous functions. First, in some embodiments, the tool 100 can provide a carrying function in that, when moving material over a distance, the forward corners 113 being swept forward relative to the middle front portion 114 directs material inwardly, which can result in less spillage. Second, in some embodiments, the tool 100 can provide a folding function in that, when cutting material with the leading edge 112 of the blade 110, the aggressive forward sweep of the blade 110 helps fold material from the forward corners 113 toward the middle front portion 114. Third, in some embodiments, the tool 100 can be used to form a convex ground surface, such as the transition from a road to a ditch shape. In some embodiments, for example, the coupling element 120 can be configured to tilt the blade 110 forward about a horizontal axis H that is substantially perpendicular to the centerline C of the tool 100 and/or the primary direction of travel D, the forward corners 113 of the blade 110 can be arranged to cut at a deeper depth into a ground surface G than the middle front portion 114 (See, e.g., FIG. 5A), and thereby a ditch-line or another convex surface can be achieved.

Further, when the blade 110 is set flat on the ground and viewed from directly above, such as is shown in FIG. 2 , the trailing edge 116 is convex in shape in relation to the primary direction of travel D. In contrast to the leading edge 112, a middle rear portion 118 of the trailing edge 116 extends farther from the horizontal axis H relative to rear corners 117 of the trailing edge 116. In some embodiments, the convex shape can be formed as a constant radius curve, in which the radius relates to the total width of the blade 110 in a ratio that ranges from about 4 to about 7, depending on how aggressive the blade is for forming concave shapes. In this regard, for a representative blade width of 8 feet, the convex trailing edge 116 can follow a curve with a radius in a range from about 32 feet to about 56 feet. In some embodiments, the convex shape is symmetrical with respect to the centerline C of the tool 100. The convex portion of the blade 110 may be a continuous curve or it may be formed by a series of flat surfaces to facilitate wear surface manufacturing and replacement.

This convex trailing profile can likewise provide several functions. First, in some embodiments, the trailing edge 116 can provide depth control for the leading edge 112. As the blade 110 is pushed forward into material to be graded, the material adds to the effective weight of the blade 110 and can rapidly pull the blade 110 down beyond available tractive effort and stall out forward motion. By controlling the coupling element 120 to orient the blade 110 such that the trailing edge 116 is very close to a depth of the leading edge 112, however, the blade 110 can be easier to control and less likely to develop such inadvertent gouging of material. Second, in some embodiments, the trailing edge 116 can be configured for spreading material. For example, by setting the trailing edge 116 below the leading edge 112, a controllable amount of material can flow under the leading edge 112 and is “smeared out” by the trailing edge 116. This arrangement of the blade 110 also allows for a faster travel speed, as the leading edge 112 is prevented from contacting the ground except for raised defects to be planed off. Third, in some embodiments, the coupling element 120 can be configured to tilt the blade 110 progressively rearward along the horizontal axis H, up to and including being oriented perpendicular to the primary direction of travel D. In any such rearwardly-tilted orientation, the middle rear portion 118 of the trailing edge 116 of the blade 110 can be arranged to cut at a deeper depth into the ground surface G than the rear corners 117 (See, e.g., FIG. 5B), thereby resulting in a concave shape in the graded material. Fourth, in some embodiments, the blade 110 can be configured for doing finish work or cleanup grading without leaving lines on the ground because the middle rear portion 118 can be set slightly below the rear corners 117, leaving no observable edges to the graded area.

In addition to designing the general shapes of the leading edge 112 and/or the trailing edge 116 of the blade 110, the edges of the blade 110 can be further configured to control the way in which the tool 100 engages the material to be graded. In some embodiments, for example, the leading edge 112 of the blade 110 is configured to have a positive rake angle α (i.e., an acute blade angle) that forms a wedge shape oriented toward the primary direction of travel D. In some embodiments, the positive rake angle α has a value in a range from about 45 to about 75 degrees. Those having ordinary skill in the art will recognize that, with respect to a reference plane R that is oriented substantially perpendicular to the ground surface G, a positive rake angle implies the sum of the clearance angle and wedge angle is less than 90°. As schematically shown in FIG. 6 , for example, a positive rake angle α offers a sharp cutting edge during grading. Cutting force and power requirement is comparatively less while grading with such a configuration for the tool 100, and this arrangement also helps in considerably reducing heat generation during grading. With regard to this discussion of the leading edge 112 having a positive rake angle α, those having ordinary skill in the art will recognize that this terminology is used to describe usage of the tool 100 when engaging the ground in a “forward” direction forward (i.e., in a primary direction of travel D of the tool 100). If the blade 110 was oriented in a “reverse” direction, however, the leading edge 112 (which would in that case be oriented in a trailing position) may then be operable to engage the ground in a negative rake orientation for “smearing” of the ground surface G.

In addition, as shown in FIG. 7A, when in use, the tool 100 will begin to push material in front of the leading edge 112, and it will continue to accumulate material up to the carrying capacity of the blade 110, which can provide for more aggressive material handling or dozing work. When the carrying capacity is exceeded, the material begins to flow over the top of the blade as shown in FIG. 7B. Those having skill in the art will recognize that the carrying capacity can vary depending on the height of the leading edge 112 of the blade 110. In some embodiments, a height of the leading edge 112 of the blade 110 has a proportional value in a range from about 6% to about 10% of the blade 110. For example, for a configuration in which the blade 110 has a width of about 8 feet, a height of the blade 110 can be in a range from about 6 inches to about 10 inches. Even for a given configuration for the blade 110, the carrying capacity can further be varied depending on a number of factors, including but not limited to the speed of travel, the incline of the ground surface (e.g., uphill vs. downhill), or the material being moved. This spill-over wedge design is in contrast to other types of earthmoving blades which have curved moldboards which resist spill-over by rolling material forward. The top of the blade 110 is shaped for unobstructed flow of material except for the attachment points for draft linkage or machine coupler points.

Allowing some degree of spillover can be advantageous in many applications relating to road maintenance. In particular, maintenance of gravel roads often involves tasks of cutting, mixing, and reapplying. A cutting step can involve reshuffling and redistributing gravel by a tool that is least susceptible to mirroring defects as it passes over them. One advantage of the concave shape is that different portions of the leading edge 112 of the blade 110 pass over a given section of the ground surface G over time, providing a “bridging” effect to help the blade 110 pass over the defects without mimicking the defects. Further, due to wear and the rinsing effect of heavy rain, the surface of a gravel road is often not an optimal composition of aggregates due to finer gravel being broken down and rinsing out or blowing away in the form of “dust” often associated with gravel roads, which can often bias the composition of the surface aggregates to larger material. A mixing step can thus be beneficial when grading such a surface by engaging the ground surface G with a deeper cut to produce a more varied mix of aggregates for filling defects. In such a step, the most efficient path for the cut and mixed aggregates is over the top of the blade 110. Finally, in a reapplying step, as the material flows over the top of the blade 110, the material spills out in a way that is inherently pseudo-random and naturally has diffused edges, disguising the exact path of the graded area in a way that can be more visually appealing than other methods.

In some embodiments, rather than the leading edge 112 having a fixed blade edge structure, the blade 110 can also have attachment points for additional “bolt on” height to increase carrying capacity before spill-over. In a further alternative, in some embodiments, the blade can be fitted with a variable height device, generally designated 130. In this configuration, the device 130 can be operated in at least two positions. Referring to an exemplary configuration shown in FIGS. 8A through 8C, in a lowered position shown in FIG. 8A, an edge extension 132 is positioned against a top of the blade 110 such that the edge extension 132 is substantially in alignment with the leading edge 112 of the blade 110 and at least substantially conforming to the concave profile of the leading edge 112. In this arrangement, the edge extension 132 effectively extends a height of the leading edge 112 to increase carrying capacity. In some embodiments, the carrying capacity is increased in this way by an amount in a range from about 200% to about 400%. In some embodiments, the edge extension 132 is a flat steel surface that is oriented at an angle of about 90 degrees with respect to the ground surface G when in this lowered position.

When an increased carrying capacity is not desired, however, the edge extension 132 can be moved to one or more raised position. For example, in a first raised position shown in FIG. 8B, the edge extension 132 is moved to be at least partially raised above the top edge of the blade 110 such that a gap is formed between the edge extension 132 and the blade 110. In some embodiments, the variable height device 130 is pivotably attached to the blade 110 such that a torque applied to the variable height device 130 results in the variable height device 130 pivoting about a pivot axis 133, which moves the edge extension 132 relative to the leading edge 112 to create a gap between the elements. Although such a pivotable arrangement is shown in FIGS. 8A through 8C, those having ordinary skill in the art will recognize that any of a variety of mechanisms can be used to selectively position the edge extension 132 adjacent to or separated from the leading edge 112. In some embodiments, movement of the variable height device 130 is achieved using hydraulic control components, although those having ordinary skill in the art will recognize that any of a variety of other mechanisms can be used for this purpose. In any arrangement, when the variable height device 130 is in the first raised position, material collected in excess of the carrying capacity of the tool 100 can spill over the top of the blade 110, allowing the blade to mix and reapply road base or other material as discussed above.

In addition, in some embodiments, the tool 100 can further include one or more ripper tool 134 that is configured to engage the ground surface G behind the blade 100. In one example configuration shown in FIG. 8C, the one or more ripper tool 134 is provided as an element of the variable height device 130 and is movable substantially in opposition from the edge extension 132. In particular, in some embodiments, when the variable height device 130 is arranged in either the lowered position or the first raised position, the one or more ripper tool 134 is positioned above the bottom of the blade 110 (e.g., above the ground surface G). The variable height device 130 can be configured to be movable to a further second raised position, however, in which the one or more ripper tool 134 is extended beneath the bottom of the blade 110 to engage the ground surface G. In this position, the one or more ripper tool 134 can be configured to break up compacted materials and further mix the ground materials.

In some embodiments, the variable height device 130 can be provided as a plurality of independently-operable devices to provide more discrete control over which portions of the blade 110 enable spillover. Referring to FIG. 9 , for example, in some embodiments, one variable height device 130 is provided on either side of the blade 110. In such a configuration, both devices can be operated in unison to selectively control the tool 100 to either allow spillover across the entire blade 110 or increase a carrying capacity as a whole. Alternatively, the device on one side can be raised and the other lowered to provide variance in carrying capacity, which in some situations can tend to shunt or “fold” material from one side and spill it over on the other side. In this way, the operator can bias the spill over to one side versus the other to direct material to one area of the road so that a specific profile, such as a crowned road, can be effectively created with a minimum of passes.

In contrast to this wedge-shaped configuration of the leading edge 112, in some embodiments, the trailing edge 116 has a negative rake angle β (i.e., a blunt blade shape). As schematically shown in FIG. 10 , for example, a negative rake angle β presents an obtuse and/or rounded shape that requires downforce to push its shape through material. Any of a variety of values for the negative rake angle β can be effective for “smearing” material under the trailing edge 116. In some embodiments, for example, a 90 degree edge angle relative to the ground surface G (i.e., negative rake angle β of about 0 degrees relative to a reference plane R) can provide an effective wear surface that is easy to manufacture and replace. Those having ordinary skill in the art will recognize that the negative rake angle β offers a strong tool tip, which makes the tool more resilient under impact loading. It also resists plastic deformation at high cutting temperature because of the thick cutting edge which can absorb and at the same time dissipate more heat. This negative rake configuration for the trailing edge 116 can provide particular benefit for certain finish grading applications or working at higher ground speeds since the “smearing” function of the trailing edge 116 allows finish work to be completed without leaving lines on the ground.

As discussed above, to adjust an angle at which the blade contacts a ground surface and thereby enable the multiple operating positions discussed above, the coupling element 120 is connected to the blade 110. In some embodiments, the coupling element 120 includes a two-axis hinge point 121 that connects the blade 110 to an attached support structure and/or control elements and transfers force from the support structure while allowing the blade 110 to be maneuvered in relation to a machine/draft linkage. In some embodiments, adjustment of this angle is achieved using hydraulic control components, although those having ordinary skill in the art will recognize that any of a variety of other mechanisms can be used. The coupling element 120 allows the blade 110 to pitch forward or rearward, such as to selectively create contact with the ground surface by the leading edge 112 or the trailing edge 116, respectively.

In some embodiments, the coupling element 120 is also configured to hinge along a secondary axis 122 (e.g., about and/or substantially parallel to the centerline C of the tool 100) to allow the blade to tilt side to side. In some embodiments, the tilt function works though a biasing element (e.g., a large coil spring) to allow some flex during operation and to cushion against shock loads. Referring to the embodiment shown in FIGS. 11A and 11B, for example, a coil spring 123 is fitted with a pin 124 on each end that allows it to be captured by upwards extending tabs 125 built into the coupling element 120. Above the coil spring 123 is a tilt cylinder interface link 126 with tabs extending downward that also captures the pins 124 on either side of the coil spring 123. In some embodiments, the tilt interface link 126 is held at a consistent radius in relation to the coupling element 120 by two bolts 127 that reach down to collars around the main pin (i.e., hinge point 121).

In operation, as shown in FIG. 12 , a hydraulic cylinder 128 is connected between the coupling element 120 (e.g., via the tilt cylinder interface link 126) and the blade 110, such as at an attachment point 129 that extends from an edge of the blade 110. In this arrangement, when the tilt function is used, force is directed into the interface link 126 and then through the coil spring 123 and into the coupling element 120. If an opposing force resists the tilting motion beyond a predetermined threshold, the tilt interface link 126 compresses the spring 123 against the opposing spring tabs 125 built into the coupling element 120. The direction of the resistance determines which set of spring tabs 125 transmit compressive force. When the blade 110 is tilted without substantial resistance to the motion of the blade 110, however, the coil spring 123 transmits the force between the interface link 126 and the coupling element 120 without any significant spring compression occurring.

In another aspect, the present subject matter provides a system for grading a ground surface, generally designated 200, the system 200 including a grading tool 100 as discussed above and a draft linkage assembly, generally designated 250, which can include any of a variety of mechanical assemblies that are configured to couple the tool 100 to a machine or vehicle 300, such as by connecting the draft linkage 250 to the coupling element 120. In this arrangement, the tool 100 can be deployed from the vehicle 300 at a desired orientation with respect to a ground surface to provide the desired grading of the ground surface. Due to the rapid wear cycles in certain aggregate maintenance applications, the blade 110 and/or all of the tool 100 can be configured to quickly detach from the draft linkage 250 so that several blades can be used in rotation with restoration of wear items being performed while another blade continues production.

The means of transferring force from the machine or vehicle 300 to the tool 100 can be arranged in a variety of ways. For example, the draft linkage 250 can be provided in any of a variety of different configurations, including but not limited to a front mounted configuration, a rear mounted configuration, a boom mounted configuration, or a straddled configuration. In any configuration, the draft linkage 250 can be operable to raise and lower the tool 100 relative to the ground surface G. In addition, in some embodiments, the draft linkage 250 is operable to pitch the blade 110 forward and pitch the blade 110 rearward. Furthermore, in some embodiments, the draft linkage 250 is operable to tilt the blade 110 side to side and/or to sideshift off the centerline. In any arrangement, in some embodiments, the vehicle 300 can be any of a variety of common construction and/or general-purpose machines to which the system 200 is configured to be easily attached with little to no customization.

Referring to the embodiment shown in FIG. 13 , the system 200 is mounted as the working implement on the front of a small tracked loader. In this arrangement, one or more hydraulically-movable arms of the loader serve as an element of the draft linkage 250 that is operable to lift or lower the tool 100. In addition, the coupling element 120 couples the blade 110 to the draft linkage 250 while allowing multi-axis movement of the blade 110 to adjust the tilt and/or roll of the blade 110 relative to the ground surface.

Referring to the embodiment shown in FIG. 14 , the system 200 is mounted as the working implement attached to the rear of a truck. In this arrangement, the draft linkage 250 connects the tool 100 to the rear of the vehicle 300, and the coupling element 120 of the tool 100 couples the blade 110 to the draft linkage 250. Again in this embodiment, the combination of the draft linkage 250 and the coupling element 120 is operable to lift, lower, and tilt the blade 110 to a desired orientation relative to the ground surface.

Referring to the embodiment shown in FIG. 15 , the system 200 is provided in a configuration in which the draft linkage 250 is coupled to the machine or vehicle 300 by a skid 260 that serves as a main frame that sits on the vehicle 300 (e.g., on a truck bed), and the draft linkage 250 includes a boom 270 that connects from the vehicle 300 to the tool 100, provides the lift function for the blade 110 during grading operations, and/or provides a secure “stow” position within the footprint of the vehicle 300 during transport. In some embodiments, the skid 260 includes one or more power or control elements that are operable to adjust the position of the blade 110 relative to the ground surface, including but not limited to a hydraulic power unit, a fuel tank, a turntable that the boom is mounted on, the valve box and the battery box.

Depending on the particular configuration for the system 200, the tool 100 can be scaled and configured to function with a variety of equipment. In particular, for example, one or both of the width of the blade 110 and/or the vertical height of the blade 110 can be selected for adjusting force or tractive effort required for the application. In some embodiments, the blade 110 can be configured to have any of a range of sizes, including but not limited to having widths ranging from about 6 feet to about 12 feet and having heights ranging from about 2 inches to about 18 inches, although those having ordinary skill in the art will recognize that the particular size and/or configuration of the blade 110 can be adjusted based on the design criteria for a given application. In one example, a 10,000 pound machine with 100 horsepower might use a tool 100 having a blade 110 that is 7 feet wide and 4 inches tall, whereas a 30,000 pound machine with 300 horsepower might use a tool 100 having a blade 110 that is 10 feet wide and 15 inches tall. In addition, the weight of the tool can further influence the function of the blade. In some embodiments, for example, the weight of the blade can be selected to be directly proportional to the capacity of the machine manipulating it. Blade weights for typical applications would generally fall between 1500 and 6500 pounds.

Regardless of the particular configuration of the grading tool 100 and/or the system 200, the subject matter described by the present subject matter can be used to provide a high degree of control over a material grading process by manipulating a single working implement. In this regard, in another aspect, the present subject matter provides a method for grading a material surface, the method including positioning a grading tool 100 at or near a ground surface G to be graded, the grading tool 100 comprising a ground-engaging blade 110 comprising a leading edge 112 having a substantially concave profile and a trailing edge 116 having a substantially convex profile as discussed above. With this configuration, the method can further include adjusting an angle of the blade 110 with respect to the ground surface G and moving the blade 110 with respect to the ground surface G to produce a desired surface configuration.

This operation can produce a variety of different surface configurations depending on the position and orientation of the blade 110. In some embodiments, for example, positioning the grading tool 100 at or near the ground surface G can include lifting or lowering the tool 100 relative to the ground surface G to adjust the height at which the blade 110 is positioned over the ground surface G and/or the amount of downward pressure applied by the blade 110 to the ground surface G. Further, in some embodiments, adjusting an angle of the blade 110 with respect to the ground surface G can include adjusting a pitch of the blade 110 about a horizontal axis H that is substantially perpendicular to the primary direction of travel D so that either the leading edge 112 or the trailing edge 116 is positioned nearer to the ground surface G. In some embodiments, the adjusting an angle of the blade 110 with respect to the ground surface G can include adjusting a roll of the blade 110 about a separate axis (e.g., about a centerline C of the tool 100) to allow the blade 110 to tilt side to side. In addition, further functions can be enabled depending on the system in which the tool is implemented. For example, in embodiments in which the tool 100 is mounted to a vehicle 300 by a boom 270 or other rotatable draft linkage 250, positioning the grading tool 100 at or near the ground surface G can include shifting the tool 100 to one side of the vehicle 300 by rotating the boom 270.

In this way, by changing the position and/or orientation of the grading tool 100 with respect to the ground surface G, any of a variety of grading tasks can be performed. In some embodiments, for example, adjusting an angle of the blade 110 with respect to the ground surface can include positioning the leading edge 112 of the blade 110 at or near the ground surface to perform “load and carry” tasks in which the tool 100 gathers material in front of the leading edge 112 up to a carrying capacity, and the material can thereby be moved from an area to be cut down to an area to be built up. In this arrangement, as long as the carrying capacity is not exceeded, the graded material stays in front of the blade 110 and can be deposited where needed.

Alternatively, in certain aggregate surface applications, the blade 110 can be loaded to capacity, and then further loading results in a continuous flow of material over the top of the blade 110. In this way, the blade 110 can mix and reapply road base or other aggregates continuously if it is paired with a vehicle or machine with sufficient tractive potential.

In another embodiment, adjusting an angle of the blade 110 with respect to the ground surface can include positioning the trailing edge 116 of the blade 110 nearer to the ground surface than the leading edge 112 to perform spreading tasks. In this arrangement, material is metered out beneath the blade 110 and can be deposited in larger lifts as desired by the operator or smeared out very thin by careful coordination of leading edge 110 and the trailing edge 116 and down pressure.

Although three modes of operation are described above, those having ordinary skill in the art will recognize that further operating modes are achievable by further manipulating the position of the blade 110 with respect to the ground surface G. In addition, functions may often be combined in a single grading pass as the tool 100 can seamlessly transition between them.

The present subject matter can be embodied in other forms without departure from the spirit and essential characteristics thereof. The embodiments described therefore are to be considered in all respects as illustrative and not restrictive. Although the present subject matter has been described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of the present subject matter. 

What is claimed is:
 1. A grading tool comprising: a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile; and a coupling element connected to the blade and configured to adjust an angle at which the blade contacts a ground surface.
 2. The grading tool of claim 1, wherein the leading edge has a positive rake blade angle.
 3. The grading tool of claim 1, wherein the trailing edge has a negative rake blade angle.
 4. The grading tool of claim 1, wherein the coupling element is configured to tilt the blade about a horizontal axis that is substantially perpendicular to a centerline of the tool.
 5. The grading tool of claim 1, wherein the coupling element is configured to tilt the blade about a secondary axis that is substantially parallel to a centerline of the tool.
 6. The grading tool of claim 5, wherein the coupling element comprises a biasing element configured to dampen rotational loads applied to the blade about the secondary axis.
 7. The grading tool of claim 1, comprising a variable height device that includes an edge extension that is movable relative to the blade between a lowered position in which the edge extension is positioned in alignment with the leading edge and one or more raised position in which a gap is formed between the edge extension and the blade.
 8. A system for grading a ground surface, the system comprising: a grading tool comprising: a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile; and a coupling element connected to the blade and configured to adjust an angle at which the blade contacts a ground surface; and a draft linkage assembly connected at a first end to the grading tool and at a second end to machine or vehicle; wherein the draft linkage is configured to move the grading tool relative to the machine or vehicle.
 9. The system of claim 8, wherein the draft linkage comprises one or more hydraulically-movable arms.
 10. A method for grading a ground surface, the method comprising: positioning a grading tool at or near a ground surface to be graded, the grading tool comprising a ground-engaging blade comprising a leading edge having a substantially concave profile and a trailing edge having a substantially convex profile; adjusting an angle of the blade with respect to the ground surface; moving the blade with respect to the ground surface to produce a desired surface configuration.
 11. The method of claim 10, wherein positioning a grading tool at or near a ground surface to be graded comprises lifting or lowering the tool relative to the ground surface to adjust one or both of a height at which the blade is positioned over the ground surface or a downward pressure applied by the blade to the ground surface.
 12. The method of claim 10, wherein adjusting an angle of the blade with respect to the ground surface comprises tilting the blade about a horizontal axis that is substantially perpendicular to a centerline of the tool.
 13. The method of claim 12, wherein adjusting an angle of the blade with respect to the ground surface comprises positioning the leading edge of the blade at or near the ground surface; and wherein moving the blade with respect to the ground surface comprises gathering material from the ground surface in front of the leading edge.
 14. The method of claim 13, wherein gathering material from the ground surface in front of the leading edge comprises stopping gathering when a carrying capacity of the blade is reached.
 15. The method of claim 14, comprising moving an edge extension into alignment with the leading edge to increase the carrying capacity of the blade.
 16. The method of claim 13, wherein gathering material from the ground surface in front of the leading edge comprises gathering material in excess of a carrying capacity of the blade to cause a flow of material over a top of the blade.
 17. The method of claim 12, wherein adjusting an angle of the blade with respect to the ground surface comprises positioning the trailing edge of the blade nearer to the ground surface than the leading edge; and wherein moving the blade with respect to the ground surface comprises spreading material along the ground surface beneath the blade.
 18. The method of claim 10, wherein adjusting an angle of the blade with respect to the ground surface comprises tilting the blade about a secondary axis that is substantially parallel to a centerline of the tool. 